1. Field of the Invention
The invention relates generally to a process for producing resinous composition surface coverings and, more particularly, to the process for forming such a product having a multi-level embossed and shaded wear surface. The embossed wear surface on the sheet includes design areas containing minute, closely spaced ink deposits, which areas are, overall, intermediate in elevation between other printed and non-printed areas of the sheet. Additionally, the non-ink-containing portions of the sheet between the minute ink deposits may be at an elevation below that of the ink-containing portions in these areas but above that of other non-ink-containing areas of the sheet. These differences in shading and elevation may be produced from a single printing element.
2. Description of the Prior Art
It is known to produce plastic sheets for floor and wall coverings, and the like, wherein the fused layer contains a thermoplastic synthetic resinous binder, plasticizers and pigments. It is also known to enhance the appearance of such sheets by means of various decorative designs thereon which may extend partially or completely through the sheet. Further enhancement of the appearance of such sheets has been accomplished by achieving a three-dimensional appearance thereon. Prior methods of doing this have included mechanical or chemical embossing techniques, or inclusion with the granules of the sheet-forming composition of an ingredient which can be subsequently removed or altered to produce an embossed effect. It is also known to obtain a textured surface on a resinous surface covering by controlling the fluid viscosity of the printing composition and/or overprinting to increase the amount of ink in selected areas of the sheet. It is further known to print on various substrates by applying the printing composition in minute separate but closely spaced deposits which, when viewed from the intended distance for vision, presents the appearance of a continuous coating. It is also known to provide a background color for the wear layer of a resinous sheet which partially penetrates the back of the layer and provides a decorative contrast and depth effect when viewed in combination with the top surface design elements which extend from the face of the sheet down into the wear layer.
U.S. Pat. No. 3,359,352-Powell el al relates to a method for forming a resinous composition surface covering having a geometric decoration. This is accomplished by depositing a layer of fine granules of resinous composition on the surface of a base which may have been previously coated with a pigmented resinous composition to hide the color of the backing and to form a good background for the printed design in the event the backing would be visible. The granular layer is then heated to sinter the granules to form a porous layer, a design is formed on the sintered layer with a printing composition which will penetrate into the porous composition. Then, by heat, with or without pressure, the printed porous layer is formed into a non-porous layer containing an inlaid design. It is further disclosed by this patent that a textured or embossed product can be obtained by controlling the fluid viscosity of the printing composition, and/or overprinting to increase the amount of ink in selected areas of the sheet, or by including with the granules a substance which, on further treatment, will create voids in the granular layer. Controlling the amount of printing composition to fill such voids controls the location and elevation of embossing.
U.S. Pat. No. 3,213,787-Miller relates to simultaneous multi-colored printing wherein there is provided on a gravure cylinder a plurality of types of image printing cavities, each type being selective of a particularly colored printing composition, the several types of image printing cavities being located on the surface in accordance with the arrangement of color ("hue") in the graphic subject matter or other colored original of which a duplicate is desired. The depth of each cavity is determined by the intensity required for that particular color at the particular point. The inks are transferred from the treated surfaces of the cylinder to the surface of the paper in a pattern established by the arrangement of the treated cavities in the cylinder surface. It is stated that it is believed that shading is achieved by the lateral flow of ink along individual fibers or between adjacent fibers of the paper which results in overlapping colored areas and makes possible the subtractive transmission of light. Surfaces which prevent the lateral flow of ink, including various films and foils may also be printed in multi-color in a single operation. In such cases, the separate small areas of ink may remain as separate dots of color, to give an impression of uniform coloring when seen from a sufficient distance. In an alternative multi-color printing process, the principles of this invention are combined with procedures and principles of Intaglio half-tone printing, in which the ink-accepting cavities are all of substantially equal depth but vary in area inversely with the intensity of the light image.
U.S. Pat. No. 2,649,386-Snowman, Jr. relates to the coating of paper wherein the coatings which are discontinuous give the appearance of being uniform. This is accomplished by applying the coating in accordance with a uniform minute pattern formed upon an applicator or coating roll. Such a pattern, for example, can comprise a minute grid design or a plurality of minute, uniformly spaced, separate depressions formed in the applicator roll surface. The resulting fine coated and uncoated areas of the paper are of such small dimensions that they are not independently readily noticeable as viewed with the naked eye at the intended distance for vision, and consequently, the paper presents the appearance of being entirely uniform with the minute dots of coating composition being substantially embedded in the paper whereby a surface will be produced having greatly enhanced printing qualities in appearance.
U.S. Pat. No. 3,259,515-Pecker relates to a method for reducing the gloss of printed surface coverings wherein the fused wear layer of the surface covering is printed with small transparent deposits of resinous printing ink spaced apart over the entire surface of the product and the ink is then dried. The area of the ink deposits determines the gloss of the product. The smaller the deposits, the higher the gloss of the product and the wider the deposits, the less gloss. The gloss, therefore, is controlled by limiting the area of original surface exposed.
In contrast to the prior processes, the present process, using conventional equipment, obtains unexpected and improved results by providing a way to achieve in-register shading and multi-level embossing on a plastic surface covering from a single printing element. The design areas printed with the minute separate, closely spaced ink deposits are, as a whole, retained, after fusion, at an elevation higher than the completely uninked areas and lower than other ink-containing areas printed in the normal manner. The surface of the dot printed areas may be rendered substantially smooth or embossed as desired by merely controlling the spacing of the minute ink deposits and their penetration into the sheet. The coaction of the color of the closely spaced ink deposits which penetrate into and are visible below the surface of the sheet, together with the increased thickness of the unprinted areas between the dots, and the background color which is visible in the completely uninked areas and between the minute spaced ink deposits further contribute to the improved aesthetic properties of the design. Thus, the process of this invention provides a relatively simple and inexpensive procedure for producing a highly decorative multi-level embossed wear surface, not obtainable using prior methods, on a resinous surface covering without the need for prior mechanical or chemical embossing techniques.